BTU
The British Thermal Unit (BTU) is a traditional unit of energy that quantifies the energy required to heat one pound of water by one degree Fahrenheit. Developed during the Industrial Revolution, it was originally used to measure the energy content of coal for steam engines. One BTU is equivalent to approximately 1,055.06 joules, the standard unit of energy in the International System of Units (SI). The BTU is particularly relevant in various industries, including power generation and heating, where it helps describe energy output and consumption. Other related units include the calorie, which measures the energy needed to raise the temperature of one gram of water, and larger units like the barrel of oil equivalent and ton of coal equivalent, which quantify the energy from specific fuels. Although the joule is now the preferred scientific measurement, the BTU remains widely used, especially in contexts such as home heating and energy production. Understanding BTUs can aid consumers and professionals in making informed energy decisions.
BTU
FIELDS OF STUDY: Classical Mechanics; Thermodynamics
ABSTRACT: The British thermal unit (BTU) is a traditional unit of energy. One BTU is equal to the energy needed to heat one pound of water by one degree Fahrenheit. It has largely been replaced by the joule.
PRINCIPAL TERMS
- barrel of oil equivalent: the energy output of burning one barrel (42 gallons, or 159 liters) of crude oil; equal to 5.8 × 106 BTU or 6.1 × 109 joules.
- calorie: the energy needed to raise the temperature of 1 gram (0.002 pounds) of water by 1 degree Celsius (1.8 degrees Fahrenheit); equal to 3.96 × 10−3 BTU or 4.19 joules.
- heat value: a measurement of the energy released as heat when a specific amount of a specific substance is burned; typically applied to fuels and foods in units of energy or mass.
- International System of Units (SI): a widely used standardized system of units for measuring natural phenomena, based on and largely identical to the metric system.
- joule: the SI unit of energy, equivalent to the work done by applying a force of one newton over a distance of one meter. One BTU is equal to 1,055.06 joules.
- therm: the energy released by burning 100 cubic feet (2.83 cubic meters) of natural gas; equal to 1.02 × 105 BTU or 1.08 × 108 joules.
- ton of coal equivalent: the energy released by burning 1 US short ton (0.91 metric ton) of coal; equal to 19.49 × 106 BTU or 21.28 × 1010 joules.
Measuring Energy
The British thermal unit (BTU) was developed during the Industrial Revolution as a way to measure the amount of energy contained in the coal used to power steam engines. It was defined as the energy needed to heat 1 pound (453.59 grams) of water by 1 degree Fahrenheit (0.556 degrees Celsius). The joule has replaced it in science as the standard unit of energy within the International System of Units (SI). One BTU is equal to 1,055.06 joules.
The BTU is one of many traditional units of energy. Another such unit is the calorie, defined as the energy needed to raise the temperature of one gram of water by one degree Celsius. It is most commonly used in chemistry. (Note that the "calories" in food are in fact kilocalories, sometimes written as Calories; one Calorie is equal to one thousand calories.) Other traditional units were developed based on the heat values of fuels such as oil, coal, and natural gas. One barrel of oil equivalent is the energy released by burning one barrel of crude oil; the ton of coal equivalent, one short ton of coal; and the therm, one hundred cubic feet of natural gas. Despite the potential for confusion, these units are still used in their respective industries. For example, therms are commonly used in home heating.
Modern Use of the BTU
BTUs are used in a number of industries, such as the power industry, to describe energy output. "BTU" may also be used as shorthand for BTUs per hour, a measure of power (energy spent over time). Despite the prevalence of the joule, the BTU is a widely accepted standard in many countries that use the metric system.
Bibliography
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"December 1840: Joule’s Abstract on Converting Mechanical Power into Heat." APS News Dec. 2009: n. pag. APS Physics. Web. 3 Apr. 2015.
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